This invention relates to oil burners and more particularly to one which provides an intimate mixing of fuel and air to enhance operating efficiency.
In the operation of oil burners, including the relatively compact units used for home heating, there has been a problem of breaking the oil into particles fine enough to enable efficient combustion with acceptably low generation of soot and noxious exhaust gases, such as carbon monoxide and nitrogen oxide.
The prior art has recognized the value of vaporizing a normally liquid fuel oil to obtain increased fuel combustion efficiency and reduced production of soot and exhaust gases. However the techniques taught to achieve such results are complex, expensive, require excessive heat to vaporize the fuel oil and/or are not responsive to control to provide a range of heating levels.
An additional factor in fuel heating efficiency is the loss of heat up the stack. In order to provide an adequate mixture of air and atomized fuel oil to maximize the burning of the fuel oil, air has to be blown into the combustion chamber. The air has to be provided in a substantial excess quantity, the rule of the thumb being 20% over stoichiometric. As a consequence, the hot gases of combustion have relatively low residence time in the combustion chamber and are emitted up the stack with a temperature where an appreciable amount of heat could still be transferred to and through the heat exchanger.
Although a large number of proposals have been made to provide more complete combustion, reduced pollution and increased heat transfer from the combustion chamber to the heating fluid, the achievement of one of these objectives tends to result in a loss of the other objective.
Accordingly, it is a major purpose of this invention to provide an optimized trade-off between the seemingly conflicting objects of complete combustion, minimum pollution and maximum heat transfer.
It is a further object of this invention to provide this optimum trade-off and optimum combination of results in a device which is relatively inexpensive to manufacture, simple to maintain and substantially immune to the varied environments within which it must operate.
For an improved fuel oil burner to be employed in a large number of homes and factories, it must operate substantially trouble free and must be able to withstand a range of ambient conditions particularly with respect to temperature, dirt and other pollutants that may exist in the wide variety of environments where such a device is likely to be used.
It is also important that the optimized trade-off between the achievement of these various objectives and the optimized enhancement of each of these objectives be maintained over long periods of time throughout a range of environmental conditions. After all, if there is any rapid degradation in performance in varying environments or if delicate adjustments have to be maintained, it is unlikely that the improvement objectives will be attained as a practical matter in field use.